1. Technical Field
The present invention relates to an information storage medium, and more particularly, to a high density information storage medium which uses a metallic nano-aperture array.
2. Related Art
In general, the storage capacity of optical disks, which have been developed these days, is classified into a DVD (digital video disk) grade (4.7 GB) using a red laser and a BD (blue-ray disk) grade (25 GB) using a blue laser.
Recently, in order to store the signal flow of high density digital video as information, an information storage medium, which has capacity over 20 GB and a data transmission speed over 25 Mbps, is needed. Moreover, currently, as technology has been developed, information storing technique capable of recording information to realize the capacity of a terabyte CD (compact disk) is demanded.
In order to store information to high capacity, it is inevitably required to increase the storage density of an optical recording medium. The storage density of an optical recording medium can be increased by decreasing a record pitch.
The record pitch is proportional to the wavelength of a laser beam and is inversely proportional to the NA (numerical aperture) of an objective lens. Accordingly, in order to decrease the record pitch, a way of reducing the wavelength of a laser beam used for recording information or increasing the NA of an objective lens is mainly used.
However, the accomplishment of high density by the use of a short wavelength laser beam (a blue laser beam of 405 nm) and a high numerical aperture (NA=0.85) has theoretical and technical limits, and thus, a new way for realizing higher storage capacity is demanded in the art.